Recently, with development of the information age, research has been actively conducted into a display device and, in particular, a light emitting diode (LED) display or an organic light emitting diode (OLED) has drawn attention.
Such an OLED uses an organic material that autonomously emits light and has distinctly different characteristics from a conventional liquid crystal display (LCD), a plasma display panel (PDP), or the like. In particular, a display device using an OLED is a next-generate display device and is known as a so-called bendable display and, recently, has also been widely used as a display of various portable devices such as a cellular phone, a smartphone, and a tablet personal computer (PC).
An OLED is a device that generates an electron-hole pair in a semiconductor from an electron and a hole and emits light through a recombination procedure of the electron-hole pair. Such an OLED is capable of expressing all the three primary colors of light at a relatively low driving voltage and is excellent to realize high resolution and natural color. It may be possible to produce a large-size display device with low expense and display devices advantageously have bendable characteristics and high response speed.
However, the above OLED includes a structure including an organic thin film and an electrode and, thus, has a problem in that the OLED is rapidly degraded when external moisture, oxygen, or the like penetrates thereinto. To overcome the problem, the OLED essentially needs a passivation film that blocks moisture and oxygen.
Recently, a method of forming a passivation film formed of an inorganic material as a multiple layer via atomic layer deposition (ALD) or plasma enhanced chemical vapor deposition (PECVD) has been developed.
However, ALD advantageously has a low water vapor transmission rate (WVTR) but has a problem in that it is difficult to realize a large area and, in particular, throughput is remarkably low.
Furthermore, a passivation film formed via PECVD has a problem in that flexible characteristics are degraded due to a relatively very large thickness. In addition, when the passivation film is deposited as a multiple layer, different layers are deposited and, thus, separate apparatuses for forming the respective layers are needed, thereby increasing manufacturing costs and further increasing manufacturing time.